Published as a collection of his correspondence, Jesuit missionary Pierre-Jean De Smet’s Letters and Sketches documents his arduous 1841-1842 journey to establish St. Mary's Mission among the Flathead (Salish) Indians in the Bitterroot Valley of present-day Montana. The text provides vivid, firsthand ethnographic observations of the Rocky Mountain tribes, detailing their daily customs, buffalo hunts, and initial enthusiastic reception of Catholicism. A keen insight drawn from the letters is the profound paradox of De Smet’s mission: while he deeply admired the Indigenous peoples and frequently romanticized them as uncorrupted paragons of natural virtue, his ultimate objective was to systematically replace their traditional spiritual practices with rigid European Catholic orthodoxy. Furthermore, these widely circulated letters inadvertently acted as powerful promotional literature for westward migration, accelerating the white American expansion that would ultimately dismantle the isolated indigenous Catholic utopias De Smet had hoped to build.